This application claims the priority of Korean Patent Application No. 2003-97155, filed on Dec. 26, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a quality-of-service technology for a communication system, and more particularly, to an apparatus and method for guaranteeing quality-of-service in a wireless local area network (LAN).
2. Description of the Related Art
A voice-over-Internet protocol (VOIP) technology represents an IP telecommunication technology used when a plurality of facilities transfer voice information using an IP. In general, the VoIP technology deals with not a conventional protocol based on circuit as used for a public switched telephone network (PSTN) but a protocol for sending voice information with a digital format in discontinuous packets. Therefore, since packet transmission is discontinuously achieved, it is difficult to guarantee quality-of-service (QoS).
The QoS of voice information must be guaranteed for VoIP services. Accordingly, an IEEE 802.11 wireless LAN media access control (MAC) technology has recently been suggested as a new LAN technology for guaranteeing the QoS.
However, the IEEE 802.11 MAC technology cannot support frames to which discriminated user priorities are applied. Basically, when a channel access right is granted, a distributed coordination function (DCF) provides the same proportional channel access right to all stations contending for channels in a basic service set (BSS). However, the same proportional channel access right is not preferable for stations having different user priorities. Therefore, from the point of view of the QoS, the MAC technology must discriminately deal with frames having different priorities and provide a QoS field included in a frame header.
To provide these functions, an enhanced distribution coordination function (EDCF) has been included in an IEEE 802.11e standard work. The EDCF provides a discriminated distribution channel directly to each frame having 8 user priorities. The 8 user priorities are mapped to 4 access categories (ACs), and an IEEE 802.11e station must realize all of the 4 ACs.
However, when a terminal for the VoIP is realized, since the terminal can be sufficiently realized with an AC for a voice frame and an AC for a general use, a method of effectively using the ACs without realizing all the 4 ACs is necessary.